Melt-quenching of artificial metallic interlayer enables a resistance-free garnet/lithium interface for all-solid-state lithium-metal batteries

Garnet-type solid electrolytes are by far one of the most promising candidates for all-solid-state lithium-metal battery (ASSLMB) applications owing to their high electrochemical stability and ionic conductivity, but their practical performance is hindered by a poor interfacial compatibility with metallic lithium. Despite extensive efforts devoted to improving the garnet/lithium interface, inadequate success has been made towards commercializing ASSLMBs owing to the lack of both materials and techniques for efficient interfacial modification. In this work, we report the complete elimination of such interfacial resistance by applying an ultra-thin CuzSnyOx (6/5 < z/y < 3) layer to the garnet-electrolyte surface via a facile and scalable melt-quenching approach. Experimental and computational results show that a strong synergistic effect between Cu and Sn facilitates the formation of a uniform CuzSnyOx coating layer on the garnet electrolyte, resulting in stable lithium plating/stripping at the interface of LLZTO/CuzSnyOx with the lithium metal for 4000 hours without a short-circuit. After the interfacial resistance is eliminated with our approach, the stability of the modified garnet electrolyte is solely dependent on the intrinsic property of the garnet electrolyte itself, which brings about a high critical current density of 15.2 mA cm–2 at 60°C. We demonstrate an all-solid-state full cell containing the modified garnet electrolyte and a LiNi0.8Mn0.1Co0.1O2 cathode that had 94% capacity retention after 1000 stable cycles at room temperature.